Decelerometer



R. J. ALDEN DECELEROME'IER Dec. 11, 1934.

INVENTOR Rae/mm JALms/v ATTOI ZMs'YSa' Filed April 2, 1932 Patented Dec.11, 1934 UNITED STATES PATENT OFFICE Claims.

This invention relates to decelerometers of the general type disclosedin my copending application Ser. No. 526,603 filed March 31, 1931. Amongthe objects of the invention is to provide an instrument of thischaracter so constructed as to make possible a relatively high degree ofuniformity in the instruments as manufactured and at the same timepermit of their being sold at a price well within the means of every carowner. These objects are accomplished by the form, arrangement andmanner of assembly of the parts which in themselves possess advantagesas will more fully appear from the following specification and claims:

In the accompanying drawing which illustrates one embodiment of myinvention;

Fig. 1 is a front view of the instrument,

Fig. 2 is a side view,

Fig. 3 is a rear view.

Fig. 4 is a section substantially on line 4-4 of Fig. 1,

Fig. 5 is a, a plan view partly in section of the structure as shown inFig. 3,

Fig. 6 is a section substantially on line 6-6 5 of Fig. 4,

Fig. 7 is a plan view of a blank from which one of the elements isformed,

Fig. 8 is a side view of the element formed from the blank of Fig. 7,

Fig. 9 is a plan view of the tube closure element, and

Fig. 10 is a diagrammatic view showing the electric circuit.

Referring to the drawing the instrument comprises a casing 1, preferablymade of molded bakelite or the like, and provided on its face withwindow openings 2 and 3, respectively fitted with red and green panes 4and 5 of celluloid, glass or other suitable material. The casing 1 is inthe shape of a cylindrical cup, open at the back, and the windowopenings are each surrounded by inwardly projecting open ended cylinders7, formed integral with the casing, which cylinders are of slightlylarger diameter than the windows thus providing annular shoulders 8against which the panes 4 and 5 fit as shown in Fig. 5. The panes may bemade of a diameter to be held in position against the shoulders 8 byfrictional en gagement with the walls of the cylinders '7 or 50 they maybe held in place merely by engagement with electric light bulbs 10,annular felt or rubber cushions 6 being interposed between the bulbs andthe panes as shown in Fig. 5. The bulbs 10 are held in the cylinders 7by a metal cross bar 11 formed as shown in Fig. 7 with circular portions12. The circular portions 12 are of a diameter, and are so spaced on thebar 11 as to fit in the inner ends of the cylinders 7 and are providedwith central cross cuts 14 permitting the bending outwardly of points 15adapted to frictionally engage the threaded sides of bases 16 of thebulbs as shown in Fig. 5. The edges of the cylinders are notched as at1'7 to receive the bar 11, said notches preventing sidewise displacementof the bar. One end of bar 11 is extended and bent at right angles tothe bar to form an electrical connection 18 which may be grounded aslater described.

Intermediate the cylinders '7 and positioned diametrically of the casing1 is a frame 20 in the general form of a truncated right triangle havinga vertical side 21, parallel sides 22 and 23 extending at right anglesto the vertical side 21 and connected by inclined member 24. The frameis preferably made of molded bakelite or the like and is so proportionedthat the sides 22 and 23 frlctionally engage the sides of the casing lto hold the frame in position. The inner face of side member 24 of theframe is formed with an integral lug or shoulder 25 which engages thebar 11 intermediate the cylinders 'l to hold the bar, and thereby thebulbs and panes, in place.

A generally triangular channel 2'7 is molded in one side face of theframe and extends completely around the frame. The cross section of thechannel is shown in Fig. 6, the bottom of the channel beingsubstantially semi-circular as at 28 and terminating at its edges inflat shoulders 29 from which parallel side walls 30 extend outwardly tothe side face of the frame. The bottom portion 28 of the channel isadapted to be covered, to form a closed endless tube, by a flat member32 conforming to the shape of the channel and resting on shoulders 29.Member 32 is formed of some non-conducting material such as fibre orbakclite and is held in place by means of a non-conducting material 33which is poured, in plastic form, between the walls 30, and on top ofmember 32, and permitted to harden.

Before the channel 2'7 is closed by member 32 and sealed as abovedescribed a measured quantity of mercury 35 may be placed in the channelor the mercury may be inserted after the channel is closed, as laterdescribed. Member 32 is provided with an opening 37 positioned in thevertical member 21 of the frame and with spaced opening 38 and 39positioned in the inclined member 24. Through these openings are passedelectrical contact members 40, 41 and 42 respectively and these contactmembers are sealed in and held in place by the material 33.

As willbe clear from Fig. 4 the amount of mercury is made such and thecontact members 40, 41 and 42 are so positioned that when the instrumentis mounted with member 21 of the frame vertical, the level of themercury in member 21 is above contact 40, in other words contact 40 isimmersed in the mercury, while the level of the mercury in the inclinedmember 24 is below both contact 41 and 42.

Contact member 40, as best shown in Figs. 3 and 5, makes a springcontact as at 45 with the filament lead of the base of the bulb behindthe red pane 4, while the contact member 41 makes a similar contact asat 46 with the bulb behind the green pane 5. The cross piece 11 whichconnects with the threaded sides of the bulb bases is grounded, aspreviously stated, by any suitable lead such as a wire, not shown, tothe frame of the car, and through which it connects to one pole of thebattery. Contact member ,42 is connected by any suitable conductor tothe other pole of the battery.

Assuming the car'to be running at a uniform speed the condition of theinstrument is illustrated in Fig. 4, where contact 40 is immersed in themercury but contacts 41 and 42 above the mercury level so no currentflows to either light.

A sudden application of the brakes, arresting the forward movement ofthe car will cause the mercury, due to its inertia, to rise in theinclined tube, with the result that the mercury engages contact 42 whilethe mercury in the vertical leg of the tube is also still in contactwith the mercury, thus establishing a circuit from the battery throughcontact 42, mercury 35, contact 40 to the red bulb 10 and throughgrounded bar 11 to the other pole of the battery. If the brakes of thecar are in proper order the lighting of the red light is only momentaryas the deceleration will cause the mercury to leave contact 40 entirelyand cause it to rise into engagement with contact 41 thus closing thecircuit from the car battery through contact 42, the mercury 35, contact41 to the green bulb and through grounded bar 11 back to the battery.The lighting of the green signal lamp therefore indicates a properoperation of the brakes'while its failure to light and the continuedburning of the red signal-indicates an insufficient rate of decelerationand defective brake operation. In order to provide means for insertingthe mercury and also to permit adjustment of the degree of movement ofthe mercury in response to a givenrate of deceleration, a vent 50 ispreferably tapped at the base of the inclined portion of the mercurytube and the vent provided with a closure screw 51 which may be of alength such that when turned inwardly the screw tends to obstruct themovement of the mercury, in the tube, the degree of the obstructionvarying the degree of movement of the mercury in the inclined tube inresponse to a given rate of deceleration. The vent 50 also permits theaddition of more mercury or its removal if a change in amount isrequired.

The construction described offers many manufacturing advantages. Casing1 and frame 20 may be molded from bakelite at small expense, the contactmembers including bar 11 may be stamped from sheet metal. The assemblyis quickly accomplished without requiring any substantial skill on thepart of the workman. The apertures 3'7, 38 and'39, accurately fix theposition of the contact members '40, 41 and 42 and when a me sure a unt0? W W has been fi d in groove 2'7, and member '32, with the contactssealed into the groove by the plastic material 33, frame 20 becomes aunit and the instrument is completed by dropping the panes 4 and 5 intothe cylinders 7, sliding the light bulbs into the cylinders and forcingthe frame 20 into the casing 1 with shoulder 25 engaging bar 11.

It will be understood that while for the purpose of illustration aspecific arrangement of the electrical contacts within the mercuryswitch has been described to operate the light in a specific manner, thepresent invention is not limited to such arrangement but is directedbroadly to the manner of supporting and assembling the casing, panes,light bulbs and mercury switch, and that the switch, may be soconstructed, as respects tion of the contacts to the bulb terminals, toprovide any desired sequences of operation or nonoperation of the lightwithout departing from the-scope of the invention. What I claim is:

1. An instrument of the character described which comprises acylindrical casing formed of non-conducting material, said casing beingopen at the rear'and provided on its front face with two spaced windowopenings, cylindrical members projecting inwardly'from'said opening, apane of transparent .material and an electric light bulb supportedineach of said cylindrical members in alignment with the adjacent windowopening, a bar bridging the inner ends of said cylindrical members toretain the panes and bulbs within said members and forming an electricalcontact with both said lights, a generally triangular, hollow framefrictionally engaged within the casing intermediate said cylindricalmembers, means carried by the frame and engaging the bar to retain thelatter in place, a quantity of mercury within the hollow of the frame, acontact member extending through the wall of the frame andnormally incontact with the mercury and connected in circuit with one of saidlights, a second contact member extending through the wall of the framenormally out of contact with the mercury and connected in circuit withthe second of said lights and a third contact member extendingthroughthe wall of the frame at a point intermediate said first andsecond contact members, said bar and said-third contact member beingadapted for connection to a source of electric current. I

2. A structure as in claim 1 in which th mercury container comprises anendless groove formed in one'side faceof the frame, the sides of thegroove being formed with shoulders intermediate the depth of the groove,a closure member engaging said shoulders to form the bottom of thegroove into an endless tube for the mercury, apertures inthe closuremember to support the electrical contact members in their predeterminedrelation in the tube and means to seal the closure members, and thecontactmembers supported thereby, in thegro'ove.

-3. A structure as in claim 1 including a screw threaded into the frameand projecting intothe mercury .containinghollow of the frame to providean adjustable obstruction to the free movement of the mercury therein. I

4. An instrument of the class described which comprises a cylindricalcasing formed of non- .conducting material, said casing being open atthe rear and provided on itsfront face with spaced window openings,cylindrical members projecting inwardly from said openings and adaptedto support a pane of transparent material and an electric light bulb inalignment with each of the window openings, a metallic bar bridging theinner ends of the cylindrical members adapted to retain the panes andlight bulbs in position, said bar forming an electrical connection toone filament terminal of the light bulbs, a generally triangular framefrictionally engaged within the casing intermediate the cylindricalmembers, said frame having means engaging the bar to hold the latter inassembled position, a closed tube formed in the frame, a predeterminedquantity of mercury enclosed in the tube, two spaced electricalconnections positioned in the tube and formed to respectively connect tothe second filament terminal of the respective light bulbs and a thirdelectrical connection positioned in the tube, the amount of mercury inthe tube and the spacing of the three connections in the tube being suchthat movement of the mercury will close the circuit between diiferentcombinations of said electrical connections in said tube in apredetermined manner dependent upon the extent of the movement of themercury in the tube.

5. An instrument of the class described which comprises a casing formedof non-conducting material, said casing being closed in front and openin the rear and provided with two windows in its front, an electriclight bulb adjacent each window, a generally triangular, hollow framefitted within said casing intermediate said windows, a metal bar holdingthe electric bulbs and forming a common electrical connection to onefilament terminal in each of said bulbs, means on said frame forpositioning said bar, a quantity of mercury within the hollow of saidframe, two spaced electrical connections positioned within the hollow ofsaid frame and formed to connect respectively with the remainingfilament terminal in each of said bulbs, and a third electricalconnection positioned within the hollow of said frame, the amount ofmercury and the spacing of the three electrical connections within thehollow of said frame being such that movement of the mercury will closethe circuit between different combinations of said electricalconnections within said frame in a predetermined manner dependent uponthe extent of the movement of the mercury within the said frame.

REGINALD J. ALDEN.

